Amarchinta H.K.,Wright State University |
Grandhi R.V.,Wright State University |
Clauer A.H.,LSP Technologies, Inc. |
Langer K.,U.S. Air force |
Stargel D.S.,U.S. Air force
Journal of Materials Processing Technology | Year: 2010
Laser peening (LP) is a surface enhancement technique that induces compressive residual stresses in the surface regions of metallic components to increase fatigue life. Simulation of the LP process is a complex task due to the intensity of the pressure loading (order of GPa) in a very short time period (in nanoseconds). A finite element technique is used to predict the residual stresses induced by the LP process. During the LP process, strain rates could reach as high as 10 6 s -1, which is very high compared to conventional strain rates. A reliable material model is needed to determine the dynamic response of a material. In this work, an optimization-based approach is developed to obtain the material model constants when there is very little or no experimental data of material behavior available. The approach is presented by comparing the residual stress prediction from simulation with available experimental results for Ti-6Al-4V material. To demonstrate the consistency of the approach, LP experiments have been performed at LSP Technologies on Inconel ®718 with different laser power densities, and the residual stress results are compared with the simulation. The Johnson-Cook, the Zerilli-Armstrong, and the Khan-Huang-Liang material models are used during the simulation procedure. The performance of each model is assessed by comparing the residual stress results between simulation and experiments. © 2010 Elsevier B.V. All rights reserved. Source
Agency: Department of Defense | Branch: Defense Advanced Research Projects Agency | Program: SBIR | Phase: Phase II | Award Amount: 1.00M | Year: 2014
Aerospace manufacturers are using composite structures in aircraft and they are the future of aviation. Composites reduce weight and maintenance costs. Today, many composite structures are joined together with fasteners. However to meet future design r
LSP Technologies, Inc. | Date: 2010-12-07
The invention relates to a method and apparatus for improving properties of a solid material by providing shockwaves there through. Laser shock processing is used to provide the shockwaves. The method includes applying a liquid energy-absorbing overlay, which is resistant to erosion and dissolution by the transparent water overlay and which is resistant to drying to a portion of the surface of the solid material and then applying a transparent overlay to the coated portion of the solid material. A pulse of coherent laser energy is directed to the coated portion of the solid material to create a shockwave. Advantageously, at least a portion of the unspent energy-absorbing overlay can be reused in situ at a further laser treatment location and/or recovered for later use.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 750.00K | Year: 2008
Since the inception of laser peening, improved nondestructive test methods and sensors have been sought to ensure that laser peening produces the desired magnitude and depth profile of residual compressive stress in the part being treated. There are no reliable nondestructive evaluation (NDE) techniques generally applicable to any surface enhancement process to monitor residual stress, so it is important to have real-time process controls and monitors in place for these processes. Laser beam diagnostic sensors are used typically to verify that the correct laser pulse energy, temporal pulse width, and fluence spatial profile are delivered to the part for each laser spot applied. Test coupons, such as Almen strips, may be processed on a sampling basis, which provide a semi-quantitative measure of the effectiveness of laser peening. However, these techniques do not provide information measured from physical phenomena directly in the part during laser peening. Incorporating real-time process sensors, which monitor the laser beam interaction or the stress wave generated in the part on a spot-by-spot basis, will greatly reduce the probability of nonconforming process conditions. The real-time quality control system to be developed in this program will enable immediate corrective actions during processing, when needed.
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase II | Award Amount: 1.33M | Year: 2008
The U.S. Army is evaluating laser peening technology in support of major helicopter programs, including the AH-64 Apache, UH-60 Black Hawk, and CH-47 Chinook fleets. The Army has a critical need to boost the engine horsepower for these helicopters, especially when operating in high altitude theaters such as Iraq and Afghanistan. Laser peening offers a method of increasing the fatigue performance and damage tolerance of these components without increasing the size or the weight of the propulsion system. Laser shock peening has been demonstrated to significantly increase the fatigue life of metallic components by the introduction of deep compressive residual stresses. The U.S. Army utilizes numerous fatigue-critical components, which potentially could be improved by laser peening. The overall objective of the work proposed in this SBIR II program is to develop, optimize, and demonstrate laser peening technology specifically for rotorcraft materials and components, such as carburized steels for gear applications. The results from the Phase I program and the LSPT’s subsequent work with bend fatigue tests and component tests indicate that a very significant benefit from laser peening can be achieved when laser peening gears, and is driving the extension of this work to advanced rotorcraft gear steels.